Paste-dispensing syringe for medical purposes



Jan. 9, 1951 w. R005 2,537,550

PASTE-IiISPENSING SYRINGE FOR MEDICAL PURPOSES Filed Oct. 20, 1947 Patented Jan. 9, 1%)51 PASTE-DISPENSING sYin GE Fort MEDICAL PURPOSES Walther Roos, Basel, Switzerland Application October 20, 1947, Serial No. 780,778 In Switzerland October 20, 1946 1 Claim. (01. 128-218) f 1 My present invention relates to improvements in paste-dispensing syringes for medical and more particularly dental' injection purposes of the type comprising a paste-containing bush or tube which may be introduced into and withdrawn from the syringe case, means for locking the said bush in the latter, an extrusion nozzle mounted in one end of the said case and to which a conventional injection needle may be secured, and a manually operated plunger adaptedtoforce the paste out through the said nozzle.

The main object of the present invention is a paste-dispensing syringe comprising a case having an inwardly shouldered end portion, an insertable and withdrawable longitudinal bush or tube containing the paste and having a loose fit in the case, means for locking the said bush in the latter, an extrusion nozzle having a concave head-face and adapted to be seated axially non-displaceable and non-rotatable on the inwardly shouldered portion in the case and provided with a threaded extension for securing an injection needle thereto, a plunger movable in the said bush and provided with a concave press-face to engage the said paste, and a manually operated rod adapted to engage the said plunger for extruding the paste from the said bush and the said nozzle.

A further object of my improvements is to do away with the conventional screw means, packing means, and stuffing boxes which render the filling or refilling of paste and the replacing of the paste-containing tubes difiicult, and which, further, require a lot of time for the assembling and dismanteling of the syringe.

A still further object, closely related to the main object, is to so adapt the operative face of the plunger on the one hand, and the inside end of the said extrusion nozzle on the other hand as to enable the operatorwithout exerting any excessive pressure--to force the paste out through any conventional needle secured to the said nozzle without having any loss of paste at the operative face of the plunger and without using conventional packings.

I attain these and related objects by the syringe shown, in one form of invention, in the accompanying drawing, in which Fig. 1 is an elevation of the syringe parts and portions ready for assembly,

Fig. 2 a longitudinal section through the assembled syringe,

Fig. 3 a cross-section of the plunger, and

Fig. 4 a cross-section of the syringe-head on line IV-IV of Fig. 2.

- Two conventional annular finger grips a are secured to the cylindrical case a of the syringe. The extrusion nozzle 1), having a central bore 12 is provided with a concave press-face b facing the pressure space or paste chamber, and at its other end has a threaded extension b adapted to receive the injection needle. The latter may be of any conventional type. Nozzle b is introduced into case a from above, and is secured in the direction of thrust by the collar or shoulder b contacting theshoulder in the case as seen in Fig. 2, and against rotation by the flattened portions b (Fig. 4) in the correspondingly adapted bottom aperture of case a.

The cylindrical bush d, which contains the paste, is open at both ends, and is also introduced through the top aperture of case a. Bush d is provided with a circumferential groove d which is adapted to be engaged by a springloaded headed pin a disposed in a housing secured to case a.

The plunger e has a concave press-face e and is longitudinally fluted at e (Fig. 3) It is comparatively long so as to avoid a canting thereof. Plunger e thus is afforded a quiet and uniform stroke in bush (1 which contains the paste to be dispensed. The plunger rod 1 has a foot-stud f engaged in a corresponding bore e of plunger e, and a thumb-abutment (Fig. 1).

In the case of paste-syringes of prior art, the physician or dentist had to keep in store, for each of the numerous pastes required, a number of filled tubes or ampules. Prior syringes of this type further do not permit of extruding the paste through narrow-bore ducts or canals. For example, the use of an injection needle of finest canal-diameter, such as is present in any dental practice, is not possible by means of such prior syringes, because the latter would require extremely high pressures, so that the paste would extrude rearwardly of the plunger, soil the syringe, and be wasted for the major part. Very fine injection needles, therefore, cannot be used practically in such prior syringes. The latter had to be provided with special cannulae of comparatively large cross-section in order to avoid an excessive pressure in the press-space and thus an extrusion of the paste into the space rearward of the plunger.

By virtue of the concave adaption of the pressfaces according to my present invention, the pressure maximum appears to shift to the center of the press-space, While the pressure on the bush-engaging rim of the press-faces appears to be decreased, thus affording a positive seal-i 3 iiig of the plunger and a uniform rate of discharge of the paste into the hollow needle secured to the extrusion nozzle. At any rate, the extrusion of -paste in a syringe according to my present invention, even when using the finest hollow needles, is done smoothly and continuously under comparatively low pressures.

The present syringe is assembled and dismantled without screwing, packing and passing parts through stuffing boxes. In practice, the physician will dispose of a number of bushes or open-ended tubes which he readily may fill with the desired paste himself and then introduce same into the syringe.

What I claim is:

A paste-dispensing syringe for dental injections or the like comprising a casing, said casing having aninternal shoulder formed at an end thereof, a longitudinal tube for containing the paste slidably inserted in said-casi ng-, a nd having a loose fit therein, means for locking said tube in said; casing, an extrusion nozzle in said casing having a peripheral flange thereon, said peripheral flange being inserted between said shoulder and said tube in said casing, said flange being irregular in shape whereby said nozzle upon insertion in said casing isnon-rotatable and axially non displaceable, a threaded extension on said nozzle projecting from said casing and having a threaded extension thereon for securing thereto an injection needle, said extrusion nozzle having an inwardly directed concave head-face extending substantially to the internal walls of said tube, a plunger movable in said tube, said plunger having an inwardly directed concave press-face extending substantially to the internal sidewalls of said tube and adapted to engage the paste in said tube, and a rod engageable with said plunger for moving said plunger in said tube for extruding paste through said nozzle, said concave portions in said nozzle and said plunger being in direct contact with paste in said tube'coacting to concentrate maximum pressure on the paste in the center of the tube.

WALTHER ROOS.

] REFERENCES CITED The following references are of record in the file of this patent: 

